不同钙素水平对厚皮甜瓜叶片光合作用和保护酶活性的影响

采用深液流无土栽培方式,研究不同钙素水平对厚皮甜瓜叶片光合作用和保护酶活性的影响。结果表明,在缺钙、低钙、高钙胁迫下,厚皮甜瓜叶片中的叶绿素和类胡萝卜素含量明显下降,叶绿素a/叶绿素b比值升高;同时叶片中的超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)的活性及丙二醛(MAD)含量、相对电导率、可溶性蛋白质含量都明显高于正常供钙的植株。缺钙胁迫下,基础荧光(Fo)下降,低钙和高钙胁迫下Fo 升高,但缺钙、低钙、高钙胁迫下叶片叶绿素荧光参数Fv/Fm、Fv/Fo、Fm、Yield和ETR都明显下降。缺钙胁迫下叶片净光合速率(Pn)、气孔导度(Gs)下降,胞间 CO2 浓度(Ci)升高;而高钙胁迫下 Pn、Gs 下降的同时,Ci 也相应下降,表明缺钙胁迫下的光合抑制主要是由于非气孔限制引起,而高钙胁迫下的光合抑制主要是由于气孔限制引起。

Effects of different calcium levels on photosynthesis and protective enzyme activities of melon leaves

The effects of different calcium levels on the photosynthesis and protective enzyme activities of melon leaves were studied in culture solution. The results showed that under the stress of calcium deficiency,low calcium and high calcium,the contents of Chl.and caroteniod in melon leaves decreased obviously,whereas the ratio of Chl.A/Chl.b increased;At the same time,the activities of superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT),the contents of MAD and soluble protein,as well as the relative electric conductance in melon leaves were significantly higher than that of normal calcium level. The minimal fluorescence(F_o)decreaced under the stress of calcium deficiency but it increased under the stress of low calcium and high calcium. Whereas the Chl.fluorescence parameters such as F_v/F_m,F_v/F_o,F_m,Yield and ETR all decreased obviously under the stress of deficiency calcium,low calcium and high calcium. Both the net photosynthetic rate(P_n)and stomatal conductance(G_s)decreased under the stress of calcium deficiency,but the intracellular CO_2(C_i)increased; Under the stress of high calcium,P_n and G_s decreased with the decrease of C_i. It could be concluded that the inhibition of photosynthesis under calcium deficiency stress resulted from nostomatal limitation,but the inhibition of photosynthesis under high calcium stress resulted from stomatal limitation.